Self-protection for an electric type heating element, particularly heating element for washing machines, water heaters and like

Abstract: The present invention relates to a self-protection system for an electric type heating element, particularly a heating element for washing machines, water heaters and like, comprising a copper terminal element (2; 2')having a substantially extended shape, one end of which is coupled to a terminal (1; 1') of the electric heating element, within the casing (6; 6') enclosing the electric heater, a self-protection element (4, 4') for the electric heater, coupled to the other end of said copper terminal element (2; 2') in such a way that the self-protection element (4; 4') is placed externally with respect to the resistance, a ring (5; 5') outer with respect to said self-protection element (4; 4') having thermal and electric insulation properties, and a closure element (7, 9), placed in correspondence of the end of the self-protection element (4; 4') that is not coupled to the copper terminal element (2; 2') and coupled with said insulating ring (5; 5').

Description: The present invention concerns a self-protection system including a resistive electrical heater element, particularly a heater element for washing machines, water heaters and like. More particularly the invention consists in an improvement of a system of the above kind that allows to obtain a optimum protection in case of anomalous working of the electrical heater element. As it is well known, all the apparatuses providing an electric heating element, must be provided with a protection system intervening in case of anomalous working. For example, in the washing machines, the manufacturers provide that the self-protection system must intervene within a preestablished time, particularly 75 seconds, from the moment when the dry working of the electrical heater element starts, in order to avoid that the clothes within the washing machine or the adjacent plastic parts take fire. In the past, a thermofusible element out of the heater element was provided as a self- protection element. However this kind of solution had the inconvenient that did not guarantee the intervention of the said thermofusible element within the required time so that the desired effect were not always obtained. Then, solutions have been proposed that were able to overcome the above mentioned drawback, bringing the self-protection within the heating element. A first solution of this kind is for example provided in the U.S. patent N° 4,697,069 of Bleckmann, filed on August 22, 1983 and having as title: "Tubular heating element provided with overload safety means". Another solution that provides this kind of solution to overcome the drawbacks above mentioned is described in the Italian patent application N° 22892A/83, filed on September 15,1983 in the name of I.R.C.A. S.p.A Industria Resistenze Corazzate ed Affini, and having as title: "Self protected armoured electric heating element". In said Italian application a heating element is described which provides a temperature limiting device contained within the sheath that contains the heating element, and serially connected whit the resistance. However, it must be noted that in these second generation solutions, the self-protection element is very close to the heating zone, so that once the interruption is intervened, a remarkable thermal inertia verifies determining an increasing of the temperature of the body of the self-protection element. In consequence of this fact a temperature remarkably higher than the exercise temperature is present inside, so that in view of the structural features of the thermofusible element, it is out of work also after its intervention. Furthermore, an example of a self-protection system according to the preamble of claim 1 is disclosed in DE-A-4 243 894. In view of the above, the Applicant has thought and realized a technical solution that obviates all the mentioned drawbacks. In fact the solution according to the present invention provides that the self-protection element is placed again out of the external casing containing the heater element, but the coupling with the latter has been conceived and realized in such a way to be sure to fulfil with absolute certainty the intervention times provided. Therefore, with the solution according to the present invention an opportune intervention of the self-protection is obtained, without the risk that the same rearms after its intervention. It is therefore a specific object of the present invention a self-protection system including a resistive electrical heater element, particularly a heater element for washing machines, water heaters and like, which comprises a copper terminal element having a substantially extended shape, one end of which is coupled to a terminal of the resistive electrical heater element; an external casing enclosing the electrical heater element and the copper terminal element; a self-protection element coupled to the other end of said copper terminal element in such a way that the self-protection element is placed externally with respect to the external casing; an outer ring-shaped insulating body having thermal and electric insulation properties, said body overlapping the self-protection element and being connected to said external casing; a closure element placed over the end of the self-protection element that is not coupled to the copper terminal element, said closure element being coupled with said body. According to the preferred embodiment of the invention, the self-protection element is made up of a thermofusible element coupled to said copper terminal element by clinching. The present invention will be described, for illustrative, but not limitative purposes, according to its preferred embodiments, with particular reference to the figure, wherein is a longitudinal section view of the system according to the invention. Referring to the figure, the reference 1 indicates a resistive electrical heater element inside an external casing 6 of an electric heating element; the said resistive electrical heating element, here formed as a spiral, is only partially shown, the drawing showing an end part of the said external casing 6 only. The resistive electrical heater element 1 is coupled at one end of a copper terminal element 2. About the said copper terminal element is a sealing material 3. On the other end of the copper terminal element 2 a self-protection element 4 is coupled by clinching, and about said self-protection element 4 a ring-shaped hollow insulating body 5, realized with a material having good properties of thermal and electric insulation, is provided. As it can be seen from figure, the hollow insulating body 5 is partly coupled within the external casing 6 of the resistive electrical heater element 1, overlapping with the copper terminal element 2, while the self-protection element 4 is external with respect to the said external casing 6. On the outer end of the hollow insulating body 5, a metallic ring 7 or closure element is provided, said ring being moulded as an insert of the hallow insulating body 5, and external to said ring 7 a faston is welded. As it can be noted from the above description, the self-protection element 4, being external with respect to the external casing 6, does not rearm, while the kind of coupling with the resistive electrical heater element 1 allows to have an optimum activation time contrary to the prior art solutions.

Claims: Self-protection system including a resistive electrical heater element, particularly a heater element for washing machines, water heaters and like, the system comprises a copper terminal element (2) having a substantially extended shape, one end of which is coupled to a terminal of the resistive electrical heater element (1); an external casing (6) enclosing the electrical heater element (1) and the copper terminal element (2); a self-protection element (4) coupled to the other end of said copper terminal element characterised in that the self-protection element (4) is placed externally with respect to the external casing (6); an outer ring-shaped insulating body (5), having thermal and electric insulation properties, overlaps the self-protection element (4), said body is connected to said external casing (6); a closure element (7) is placed over the end of the self-protection element (4) that is not coupled to the copper terminal element (2), said closure element (7) is coupled with said body (5). Self-protection system according to claim 1), characterized in that the self-protection element (4) is made up of a thermofusible element coupled to the copper terminal element (2) by clinching. Self-protection system according to claim 1), characterized in that the closure element (7) is apt to provide a surface for mounting a faston to fasten the power supply cables of the electrical heater element (1). Self-protection system according to claim 1), characterized in that the closure element (7) is connected with the external casing (6) by the hollow insulating body (5) wich surrounds the copper terminal element (2) and the self-protection element (4). Self-protection system according to claims 1) and 4), characterized in that the space existing between the internal surface of the hollow insulating body (5) and the copper terminal element (2) is filled with sealing material (3); the aim of the said sealing material being that of preventing the resistive electrical heater element (1) and the copper terminal element (2) from moisture.

Inventors: CAPITANELLI CLAUDIO, CAPITANELLI, CLAUDIO, CAPITANELLI, CLAUDIO, MERLONI TERMOSANITARI S.P.A.
Applicants: THERMOWATT S P A, THERMOWATT S.P.A.
Application year: 1994
Main classification: H05B1
IPC codes: H05B1, H05B3, H01H37